This pilot project will continue development of an intervention (Short-term Time-limited Assertive Community Treatment) for homeless individuals with comorbid substance use and mental illness. The pilot continues research conducted by the principal investigator and co-investigators and will focus on one stage of the intervention: the treatment readiness group. The pilot will implement and test the effectiveness of the treatment readiness stage and finalize the retention protocols and manualize the group. The investigators will submit an R01 proposal to test the entire intervention in a sample of 400 homeless individuals.